1. Field of the Invention
This invention relates to a generally tubular sheathing article, e.g., a condom or prophylactic article, comprising a knitted retention structure for compressively retaining the sheathing article on the member or element being sheathed, as well as to a method of making such sheathing articles.
2. Description of the Related Art
In the field of prophylactic or condom articles, much effort has been directed in recent years to improving the structure and rate of fabrication of such articles, under the impetus of significant increases in the incidence and spread of sexually transmitted diseases, as a result of the evolution of increasingly antibiotic-resistant strains of disease-causing organisms, e.g., those responsible for diseases such as gonorrhea and syphilis, and the absence of any effective cure for acquired immunodeficiency syndrome (AIDS).
The aforementioned disease factors have also created an increased consumer demand for condoms, in view of their benefits as a safe, low cost, and generally reliable means for reducing the risk of infection and transmission of sexually transmitted diseases, as well as their traditional function as a barrier-type contraceptive means.
Against this background, design and manufacturing efforts have been focused on the develop of condoms characterized by increased ease of application to the penis of the wearer, and comfort in use, to thereby enhance the appeal of using condoms in coital activity.
Currently, most condoms are produced from a latex resin via a dipping process in which a cylindrical and rounded-end mold is dipped into a resin bath, so that the mold is coated with a thin layer of the latex material. The thickness of the latex coating on the mold is dependent on the viscosity of the latex, and the speed of extracting the mold from the latex bath. Similar latex dipping processes have been employed with suitably shaped molds to form tight-fitting gloves such as surgical gloves, as well as other sheathing articles.
Structurally, the conventional latex condom comprises a tubular main sheath with a closed distal end and an open proximal end. The open proximal end may be circumscribingly bounded by a filament of elastic material, to aid in retaining the condom on the penis of the wearer, to demarcate the proximal opening for use of the condom, and to prevent tearing of or damage to the tubular main sheath of the condom during its application and use.
In addition, the circumscribing filament serves as a "rolling core" onto which the main sheath portion of the condom may be rolled along its length in conventional fashion to produce a toroidal roll surrounding a distal end portion of the sheath when the condom is in a fully rolled conformation; subsequently, the condom is simply reverse-rolled onto the penis of the wearer, from the glans to the base of the penis.
To the extent that the elastic filament bears compressively against the circumference of the base of the penis, a further enhanced protection is provided against leakage of seminal fluid and sperm from the condom, and against entry of vaginal exudates or other coital secretions from the recipient coital partner, into the interior volume of the condom containing the penis, during sexual activity.
In order to accommodate the sealing and retention function of the elastic filament at the proximal opening of the condom, the elastic filament must be significantly stretched in application of the condom to the wearer's penis. As a result, the condom is often difficult to don, due to the small size of the condom's proximal opening, and the resistance to stretching of the proximal opening and the bounding filament which is intended to provide a tight fit once the condom is installed on the penis of the wearer.
During their commercial production, condoms made of latex rubber typically are rolled, as hereinabove discussed, to render them easier to package, store, and apply, relative to unrolled condoms. Although rolling gives the condom a more compact structure, thereby facilitating ease of packaging and storage, the donning of rolled condoms frequently is difficult since the user must stretch the roll apart in the donning operation. Generally, the "spreadability" of the rolled condom is made difficult by its tightly compacted character, and the required positioning of the rolled condom on the invariably asymmetric glans of the penis to initiate unrolling.
Further, the roll portion of the condom initially must be grasped with the fingers for application to the glans and unrolling onto the penis. The size of the condom roll is typically sufficiently small, e.g., generally being less than about 3/16 inch in roll diameter, so that it is difficult to grasp the roll with the fingertips and to install the condom on the penis of the wearer. This is particularly true in the case of very thin or form-fitting condoms which are characterized by a very tiny roll.
As a result of the small size (diameter) of the roll, the need to utilize the fingers in installation of the condom, and the absence of good grippability, the fingertips are often tightly pinched onto the roll to gain purchase thereon. This in turn raises the risk of shredding or puncturing of the condom material by the fingernails or otherwise breaking the condom as a result of such pinching or grasping, so that the condom, when subsequently unrolled, has breaks or discontinuities therein which render the condom deficient or even useless for its intended function.
The foregoing problems attendant to the use of conventional rolled condoms with elastic filament retaining rings has stimulated the development of alternative condom designs, wherein the retention structure is of a different type than elastic filaments. This effort has been made in the context of an evolution of condom technology to embrace the use of materials of construction other than latex rubber for the condom sheath.
Wheeler U.S. Pat. No. 4,964,416 discloses condoms formed of thermoplastic elastic materials such as thermoplastic elastomers, e.g., polyurethanes, polyesters, polyethers, multi-block copolymers, olefinic homopolymers and copolymers, etc. This patent discloses the use of an annular sealing element at the proximal end portion of the condom which features a circumscribed opening bounded by the annular body of the sealing element. The sealing element is formed of a thin film material, so that when the condom is donned, the inner edge surface of the annular element opening bears compressively on the external surface of the base of the penis, to provide enhanced sealing thereagainst.
Although the Wheeler patented condom provides an effective seal against the exterior surface of the penis, and the interior opening of the annular sealing element permits ready passage of the penis therethrough when the condom is installed on the penis, after installation the compressive retention force is applied to the surface of the penis only over the inner circumferential surface of the thin film annular sealing element. As a result the compressive pressure of the annular sealing element on the penis is substantial, and although the thin film annular element is radially and circumferentially yielding in character, the constrictive force exerted by the sealing element may exceed the limit of comfort, particularly when the penis being sheathed is significantly larger in circumference than the inner opening of the annular sealing element.
Considering as illustrative examples the above-discussed elastic filament retention structures of conventional latex condoms, and the annular sealing element of the Wheeler patent, it is appreciated that the compressive retention structure of a condom must satisfy several competing criteria:
(1) the retention structure must provide adequate compressive force on the penis for effective sealing of the sheath of the condom against leakage into or out of the condom sheath interior volume containing the penis, such as may compromise the contraceptive and/or prophylactic efficacy of the condom; PA1 (2) the retention structure must allow ready ingress of the penis into the sheath of the condom, which means that the retention structure must be expandable from its initial compressive or gathered state to permit the condom to be easily rolled or pulled onto the penis for installation thereon; PA1 (3) the retention structure must provide a constrictive action which however does not produce discomfort or otherwise interfere with coital pleasure and satisfaction; and PA1 (4) the retention structure must be readily securable to or formable with the sheath structure of the condom, so that the condom can be easily, quickly, and economically produced in mass production quantities--it is to be recognized that the compressive retention structure is desirably structurally consolidated with the sheath of the condom, as a unitary product article, during the condom manufacturing process, and this typically involves expansion of the retention structure prior to and/or during its being joined with the sheath, followed by relaxation of the stretched retention structure. PA1 (i) a generally tubular sheath member having a closed first end and an open second end defining an enclosed interior volume within the sheath member accessible by the open second end, for introduction of the sheathable part into the interior volume through the open second end; and PA1 (ii) a knitted retention structure associated with the sheath member at a proximal portion of the sheath member in the vicinity of its open second end, for exerting a compressive retaining action on the sheathable part at the proximal portion of the sheath member. PA1 (a) providing a generally tubular sheath member having a closed first end and an open second end; PA1 (b) disposing a circumferentially extending knitted retention band about an exterior surface second end portion of the sheath member, in spaced relation to the open second end thereof, to thereby define a proximal segment of the sheath member between the knitted retention band and the open second end; PA1 (c) everting the proximal segment of the sheath member between the knitted retention band and the open second end so that the everted proximal segment enclosingly overlies the knitted retention band; and PA1 (d) securing the everted proximal segment of the sheath member to an overlaid exterior surface region of the sheath member to form an enclosure volume containing the knitted retention band.
Considering the manufacturability factors identified in (4) above, it is apparent that the stretching of a small diameter elastic filament or 0-ring for connection to the sheath presents significant processing problems. In conventional latex condom manufacture, the retention ring is stretched over the mandrel bearing the latex sheath member (formed by drying of the latex solution applied to the mandrel during dipping thereof, as previously described hereinabove), and is positioned at a proximal part of the sheath. The condom then is rolled on the mandrel, about the elastic filament as a rolling core. In the rolling operation, a portion of the ring or resultingly formed roll may, during the rolling operation, preferentially grip or gain purchase on, the film, so that uneven tension is imposed on the sheath, which may cause it to subsequently tear or split in use. Further, the generally circular cross-section of the elastic filament and its typically very small diameter make it very difficult to gain purchase on and to position or translate with high accuracy (these are the manufacturing analogs of the purchase/manipulability use problems discussed earlier hereinabove), and these factors again may lead to the aforementioned uneven rolling problems.
The above-described Wheeler patented condom avoids the aforementioned problems incident to the use of the elastic filament as a compressive retention structure, but presents its own difficulties in the handling and processing of the thin film annular sealing element, which must of course be leak-tightly secured to the inner surface of the condom sheath to achieve its intended purpose. The thickness of the annuiar thin film sealing element may for example be commensurate with the thickness of the sheath itself, and leak-tight sealing of such low thickness films requires very accurate sealing techniques, such as heat sealing or ultrasonic bonding at low dimensional tolerances, which avoid the rupture or piercing of the films during their bonding to one another.
U.S. Pat. No. 4,855,169 issued Aug. 8, 1989 to M. W. McGlothlin et al., describes a prophylactic device including a sheath of elastomeric sheet material with a 100% tensile modulus of at least about 200 psi and a thickness of less than about 0.0014 inch. The sheath has an open end and a border containing a resilient material of reduced 100% tensile modulus, relative to the elastic sheet material. In this device, the ratio of the thickness of the border to the thickness of the sheath is from about 10 to about 300. The materials disclosed in the patent for the sheath include polyurethane and various other thermoplastic elastomeric materials. The patent discloses that the border may be constituted by a ring which is either bonded or unbonded to the sheath, or, alternatively, the border may be constituted by a flat band encircling the proximal open end of the sheath of either bonded or unbonded type.
The McGlothlin et al. patent discloses that the augmented border which is provided as the retention structure of the described prophylactic article may be formed of low modulus materials such as polyurethanes, plasticized polyurethanes, latex rubbers, silicone elastomers, ethylene/propylene thermoplastic elastomers, styrene block copolymer thermoplastic elastomers, olefinic thermoplastic elastomers, polyether block amide thermoplastic elastomers, polyvinylchlorides, acrylic-based thermoplastic elastomers, hot-melt or pressure adhesive materials, and foam polymers.
An improvement on the condom of the McGlothlin patent is disclosed in prior copending patent application Ser. No. 07/693,550 filed Apr. 30, 1991 in the name of John T. Leffler. This application discloses a condom comprising an elongate sheath having an open proximal end and a closed distal end, which is rolled or rollable on a roll ring having an axial thickness dimension and a transverse (width) dimension each of which is at least 0.125 inch, wherein the thickness of the sheath is from about 0.0004 inch to about 0.003 inch, and the ratio of the transverse width of the roll ring to the thickness of the sheath is in the range of from about 350 to about 5,000. The roll ring in such condom structure may be of a low durometer material such as a highly plasticized or solvent-swollen polymer having a gelatinous consistency rendering the sheath easily rollable thereon.
While the thrust of the teachings of the aforementioned McGlothlin et al. patent and Leffler patent application are in favor of relatively large roll rings or band structures as rolling cores, having a number of intrinsic advantages as described in these references, there is a continuing need in the art for compressive retention structures of improved type, which afford the various advantages taught to be characteristic of the McGlothlin et al. and Leffler ring and band retention structures, but which are more compact in size, and which fully meet the criteria (1)-(4) referred to and discussed hereinabove.
Accordingly, it is an object of the present invention to provide a sheath article having a compressive retention structure of improved type, affording such aforementioned advantages.
It is another object of the invention to provide a sheath article of such type, which is easily, simply, and economically manufacturable in character.
It is a still further object of the present invention to provide a method of making an improved sheath article of such type.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.